Peroxymonosulfate-diethylenetriamine pentaacetic acid composition



3,049,495 Patented Aug. 14, 1962 This invention relates to solid bleaching and cleansing compositions containing a peroxymonosulfate compound which can be effectively employed in practically any common tap water. More particularly, this invention relates to solid bleaching and cleansing compositions containing a novel combination of a peroxymonosulfate compound and a sequestering agent.

-It is well known that peroxymonosulfate compounds containing HSO such as NaHS and K50 are highly eifective bleaching compounds, being stronger oxidizing agents than hydrogen peroxide and many other commonly used per compounds. However, the use of such strong oxidizing agents in common tap water presents a problem because some tap water supplies contain manganese in amounts of about 0.1 ppm. or more. Analysis has shown that ordinary tap water rarely contains more than 0.2 p.p.m. manganese. Under the influence of peroxymonosulfates the manganese becomes oxidized to a high valence state (+3 or +4) and imparts a yellow discoloration to the object being treated. The problem especially acute when white cloth is laundered or white porcelain is cleansed. Tests have shown that as little a 0.1 p.p.m. manganese in the water will noticeably discolor White cloth or porcelain when manganese is oxidized to a higher valence state.

It has been found that manganese ions can be eifeo tively sequestered from the oxidizing action of peroxymonosulfate with diethylenetriamine pentaacetic acid (DTPA) or the alkali metal salts thereof and that these sequestering agents are not attacked by peroxymonosulfate to an appreciable extent. It has also been found that DTPA does not decompose peroxymonosulfate to any appreciable extent. Additionally, it has been determined that the monopersulfate compound and DTPA may be formulated in solid bleaching and cleansing compositions which can be added to common tap water containing substantial amounts of manganese with the result that the latter is effectively sequestered so that it will not discolor the substrate being bleached.

It is an object of the present invention to provide solid bleaching and cleansing compositions containing peroxymonosulfate that can be effectively used in virtually all tap water.

It is another object of the present invention to provide solid bleaching and cleansing compositions that contain a sequestering agent for manganese, which agent is not antagonistic to the bleaching agent.

It is still another object of the present invention to provide solid bleaching and cleansing compositions that contain a sequestering agent that will rapidly form a complex ion with manganese.

The occurrence of substantial amounts of manganese in water supplies is not unusual; common tap water will occasionally contain more than 0.1 p.p.m. manganese.

Normally, the presence of manganese is not detrimental in bleaching solutions, since conventional bleaching agents do not oxidize manganese to a yellow-colored oxidation state.

In the table below, the various concentrations of Mn++ were obtained by adding increasing amounts of manganous sulfate to distilled water and the bleaching composition below was aded to each solution. The term Oxone refers to a mixture of KHSO KHSO4 and K in mole proportions of 2/ 1/1, and KHSO the active oxygen source, constitutes about 50% by weight of the mixture.

Percent Oxone 35 Sodium sulfate 20 Sodium metasilicate 5 Sodium carbonate 20 Tetrasodium pyrophosphate 20 TABLE I Reflectance as a Function of Wash Manganese Concentrations (p.p.m.)

The cloth was given a thorough rinse after washing and then dried. After the wash and dry cycle, the reflectances of the swatches were determined in a Hunter multipurpose refiectometer using a blue filter, the fall in reflectance representing a measure of the yellowing of the fabric. The results show that even small concentrations (about 011 ppm.) of manganese are oxidized and cause yellowing.

Example 1 The same bleaching formulation containing DTPA, a white powder commercially available as Perma-Kleer 140, Refined Products Corporation, was employed under the same conditions as noted above in an amount equal to about 6% by weight based on potassium peroxymonosulfate content and the DTPA was mixed in the formulation prior to use. The water was common tap water containing about 0.2 p.p.rn. manganese. The discoloration that resulted from yellowing under identical conditions when DTPA was not added is also shown. It is to be noted that the use of DTPA caused no significant decomposition of the peroxy-monosulfate ions as indicated by active oxygen analysis.

Residual Reflectance as Function of Wash Composition of Active Table I Oxygen,

p.p.m. 1 2 3 4 5 With DTPA 16 84.0 85.8 85.6 85.4 85.4 85.5 W1th no DTPA 17 85.6 84.9 83.0 80.0 76.5 73.8

Example 2 This example illustrates the effect of DTPA when used in a cleanser. A use-worn sink was scoured with the following cleanser:

Percent Oxone 2.5 Sodium carbonate 2.5

Soap 6.0 Abrasive powder (silica or feldspar) 89.0

The cleaning was carried out using tap water containing approximately 0.3 p.p.m. manganese and the cleaned portion of the sink was allowed to stand in Water for 15 minutes between each cleaning treatment. After 8 washes a distinct yellow discoloration was apparent. On a separate section of the same sink the above formulation containing 6% DTPA (based on the weight of potassium peroxymonosulfate, the preferred source of active oxygen) was used. After 8 washes there was no visible discoloration.

In addition to diethylenetriamine pentaacetic acid, the alkali metal salts of the acid are equivalents and are also excellent sequestrants for manganese. Thus, sodium or potassium may be substituted in any or all of the five carboxyl groups of DTPA as noted in Example 3. The structures of DTPA and DTPA-5 Na are as follows:

DTPA

COzHCHg CHrCOzH N C H: C HgNCH CHgN COQHC CHgCOgH CHzCOaH DTPA-5 Na COaNaGHa CHgCO Na NC HgC HgNCH CHgN C OzNaCHz CH2COZNa CHQC O1Na Example 3 Reflectance as Function of Wash Composition ofTableI With DTPA-5 Na 86.0 87.4 87.5 86.8 87.0 87.2 87.1 87.0 86.9 With no DTPA-5 Example 4 Peroxymonosulfate can be used with a source of chloride ions as a heavy-duty bleach and as an effective Cir bleach for nylon and other synthetics. duty bleach includes:

A typical heavy- Percent Oxone 20 Sodium chloride 60 Potassium carbonate l5 Tetrasodium pyrophosphate 5 Hcavy- Reflectance as Function of Wash Duty Bleaching Solution 0 1 2 3 4 5 6 7 8 With DTPA-5 Na 86.5 86.9 86.5 85.7 85.4 84.1 83.0 82.0 80.9 With no DTPA-5 Peroxymonosulfate compounds in combination with DTPA or its equivalents can be used in a variety of bleaching, laundering and cleansing formulations. The compositions specifically set forth above are representative and should not be construed to be limiting. Ordinarily, these formulations are used in alkaline solutions. However, peroxymonosulfates in combination with DTPA can be used in either acid or alkaline solutions. Moreover, this combination can be used as a bleaching composition alone. Normally, the amount of active oxygen supplied by the peroxymonosulfate will vary from about 5 to 600 p.p.m. Throughout the specification, percentages and parts are calculated on a weight basis unless otherwise designated.

It has been found that solid bleaching compositions H and cleansers that contain an alkali metal peroxymonosulfate and DTPA and its equivalents may be added to practically any tap water without discoloring the object being treated. The amount of DTPA and its equivalents must be at least 0.01 part by weight based on each part of alkali metal peroxymonosulfate content; preferred compositions contain 0.02-0.1 part of the former to each part of the latter, although there is no critical upper limit to the amount of the sequestrant used.

The solid compositions of the present invention are stable under normal storage conditions. Contributing to the uniqueness of compositions containing the two ingredients is the fact that upon the addition of Water, neither ingredient is antagonistic to the other, and th sequestrant operates rapidly to prevent the peroxymonosulfate from oxidizing manganese. These conditions prevail throughout the relatively short time required for bleaching and cleansing.

Other common sequestering agents were not effective because they either did not prevent yellowing or reacted with the bleaching agent. Reaction with the bleaching agent would impair the bleaching effectiveness of the bleaching and cleansing compositions and is therefore unacceptable.

To be efiective, it is essential that the sequestrant have all of the desirable characteristics in solution for at least a relatively short period of time under household conditions. The outstanding sequestrant for this use is diethylenetriamine pentaacetic acid and alkali metal salts thereof. Other agents which theoretically should sequester manganese have been found to be much less eifective.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A composition consisting essentially of an alkali metal peroxymonosulfate and a compound selected from the group consisting of diethyienetriamine pentaacetic acid and alkali metal salts thereof, at least 0.01 part by Weight of said last named compound being present for each part by weight of said peroxymonosulfate.

2. A composition consisting essentially of potassium peroxymonosulfate and diethylenetriamine pentaacetic acid, at least 0.01 part by weight of said acid being present for each part by weight of said peroxymonosulfate.

References Cited in the file of this patent UNITED STATES PATENTS Reichert et al. Feb. 16, 1943 Lake et al. May 12, 1959 OTHER REFERENCES \Fried et al.: Proceedings of the Society for Ex-perimental Biology and Medicine, March 1959, vol. 100, pp.

3. A composition consisting essentially of 1 part 'by 15 P June 1953, 67106-1500- Weight of potassium peroxymonosulfate and 0.02 to 0.1 part by weight of diethylenetriamine pentaacetic acid. 

1. A COMPOSITION CONSISTING ESSENTIALLY OF AN ALKALI METAL PEROXYMONOSULFATE AND A COMPOUND SELECTED FROM THE GROUP CONSISTING OF DIETHYLENETRIAMINE PENTAACETIC ACID AND ALKALI METAL SALTS THEREOF, AT LEAST 0.01 PART BY WEIGHT OF SAID LAST NAMED COMPOUND BEING PRESENT FOR EACH PART BY WEIGHT OF SAID PEROXYMONOSULFATE. 